In recent years, it has been an international issue how to cope with the increasing demands for natural resources. In the field of resource exploration, it has become important to efficiently find natural resources (petroleum, gas, and the like) in a short period and with high accuracy. On the other hand, with a decrease in productivity of major oil fields and a decrease in the number of oil fields which can be easily explored and developed, the place of resource exploration has become deeper and the competition for exploration development has become intensified. Thus, the need for providing a high-sensitivity exploration sensor technique at a low cost is increasing. From the perspective of achieving high sensitivity, instead of a conventional resource exploration system which uses geophones, an accelerometer which uses microelectromechanical systems (MEMS) sensors is gathering attention and various accelerometers have been developed. From the perspective view of achieving high resource exploration efficiency, a technique of shortening an exploration period by increasing the scale of a sensor network system has been discussed. In this technique, it is necessary to simplify the operation of the large-scale exploration system and to decrease the cost thereof. Since a conventional cable system has a limited system scale, the use of a cableless system has been discussed to reduce the number of operation steps.
Resource exploration uses various methods depending on the phase of exploration, and a seismic reflection exploration method is known as one of major methods used to finally specify the place where resources are buried. This method involves generating an artificial vibration from an artificial seismic source disposed on an earth surface with respect to a number of vibration sensors (acceleration sensors) arranged on the earth surface, allowing the vibration sensors to receive waves reflected from respective underground layers (a soil layer, a water layer, an oil and gas layer, a basement layer, and the like), and analyzing the waveform of the wave signal to detect a geological stratum structure and a geological crust structure under the exploration target earth surface. Dynamite may be used as the artificial seismic source, and a special vehicle called an earthquake simulation vehicle capable of generating an artificial seismic source may be used. When this method is used, an earthquake simulation vehicle as an artificial seismic source, a sensor network that acquires vibration data and transmits data, and a data center (a data collection vehicle) that stores the acquired data are to be placed in an exploration target field. As described above, the conventional sensor network is configured using a communication line and a power supply line. In the cable configuration, the number of sensors that perform measurement simultaneously is limited, the installation and design is restricted due to obstacles (forest, jungle, or the like) on the field, and field facilities such as a large-capacity power facility and a large-scale data center (data collection vehicle) are required, which are one of the causes that increase the cost.